This invention relates to a process for the production of optionally foamed polyurethane plastics, particularly shaped articles, using certain denatured biomasses as reactive fillers. The fillers in question comprise biomasses based on microorganisms and the derivatives and decomposition products of microorganisms, particularly biologically purified sludges which have been deoderized and irreversibly denatured by reaction with isocyanates and/or carbonyl compounds and compounds capable of aminoplast and/or phenoplast formation.
In biological purification plants, organo-chemical effluent impurities are degraded, i.e. biologically eliminated, by means of microorganisms.
Under the conditions in purification plants, microorganisms multiply to a particularly marked extent producing a quantity of biomass consisting mainly of bacteria in the "activated sludge basin" of the purification plant which increases daily by from about 3 to 4% by weight, so that although some of the microorganisms die, the quantity of bacteria doubles in from 3 to 4 weeks. Accordingly, some of the biomass has to be continuously removed from the activated sludge basin in the form of "surplus activated sludge" in order to maintain optimal conditions for microbial effluent purification. Thus, biomasses accumulate worldwide in extremely large and ever-increasing quantities in the fully biological purification of industrial and communal effluents. In the Federal Republic of Germany alone, about two million tons (expressed as dry weight) per year of these protein-containing biomasses are presently either being dumped or burned. Also, the necessary removal of water from activated sludges still remains a problem because, under the sedimentation conditions normally applied in purification plants, the activated sludge to be removed contains only about 1% by weight of microbial dry mass. In conventional centrifuges the solids content of the sludge may only be concentrated to from 7 to 9% by weight. Even where polyelectrolytes are added and centrifuges and decanters are used, the solids content may be increased only to from 12 to 15% by weight.
Even in these low concentrations, activated sludges have a pronounced gel structure and a relatively high viscosity due to the pronounced chemical and physical binding of the water to the microorganisms. For this reason, conventional filtration is impossible without specialized treatment. Filtration is also complicated by the fact that bacteria cells attract one another and form common, slimy shells resulting in the formation of tacky flakes.
Another problem is that, as soon as it is isolated from the settling basin, the excess bacterial sludge immediately begins to putrefy and give off an intolerable odor. Even anhydrous activated sludge powder dried at 110.degree. C. has a very unpleasant odor and continues to putrefy on becoming moist. The presence of pathogenic germs remains a problem.
For these reasons, the composting of the treated sludge or its direct use as a fertilizer in agriculture are possible only to a limited extent. Even today, therefore, the elimination and utilization of treated sludges involve considerable ecological problems which, despite all efforts, have not yet been solved satisfactorily.
Two new processes have been developed which enable various biomasses based on microorganisms or metabolism and/or decomposition products thereof, including in particular the above-described treated sludges from biological treatment plants, to be worked-up in surprisingly simple and economic manner. These work-up processes are the subject of separate applications and will be described in detail later. In the present context, "working-up" means that the biomasses are concentrated, irreversibly denatured, deodorized and, in this way, made available for utilization in the plastics industry.